Difficulty linking in embind-generated bindings

[Michael....@nasa.gov]

Hello!

I’m experimenting with converting an existing project here to WebAssembly.  This project has several modules, each with its own library and test executable.  My current approach, just to see if I can get things running, is to build those test executables using the default emscripten shell.html file.  That process has been successful so far, except when I try to add a binding via embind.  Trying to “link” in the generated .js file with --post-js results in a runtime error apparently before any of the project code is run: “Module.arguments has been replaced with plain arguments_ (the initial value can be provided on Module, but after startup the value is only looked for on a local variable of that name)”

I have this relevant section of my CMakeLists file:

  add_custom_command(OUTPUT Utils-bindings.js

    COMMAND

    ${CMAKE_CXX_COMPILER}

    --bind

    “${CMAKE_CURRENT_SOURCE_DIR}/base/emscripten.cc”

    -o

    Utils-bindings.js

    DEPENDS

    “${CMAKE_CURRENT_SOURCE_DIR}/base/emscripten.cc”

    )

  target_link_options(${Utils_TEST} PUBLIC --bind --post-js Utils-bindings.js)

 

Which generates these commands:

 em++ --bind base/emscripten.cc -o Utils-bindings.js

em++  -s DISABLE_EXCEPTION_CATCHING=2 -s WASM=1 -s SAFE_HEAP=1 -s WARN_UNALIGNED=1 -fsanitize=undefined -Oz -s ASSERTIONS=1 -s DEMANGLE_SUPPORT=1 -g -Wall -fno-omit-frame-pointer -m32 --bind --post-js Utils-bindings.js @CMakeFiles/Utils-test_g.dir/objects1.rsp  -o Utils-test_g.html @CMakeFiles/Utils-test_g.dir/linklibs.rsp

Loading Utils-test_g.html in a browser produces the error.  I’ve tried all of the --(extern-)?(pre|post)-js permutations without success.  I’m well out of my depth and have been trying whatever I can find at this point.  How do I get these library bindings “linked” into the “executable”?  

Thanks!

~Michael Iatauro

[Sam Clegg]

On Fri, Jul 24, 2020 at 2:58 PM 'Michael....@nasa.gov' via emscripten-discuss <emscripte...@googlegroups.com> wrote:

Hello!

I’m experimenting with converting an existing project here to WebAssembly.  This project has several modules, each with its own library and test executable.  My current approach, just to see if I can get things running, is to build those test executables using the default emscripten shell.html file.  That process has been successful so far, except when I try to add a binding via embind.  Trying to “link” in the generated .js file with --post-js results in a runtime error apparently before any of the project code is run: “Module.arguments has been replaced with plain arguments_ (the initial value can be provided on Module, but after startup the value is only looked for on a local variable of that name)”

I have this relevant section of my CMakeLists file:

  add_custom_command(OUTPUT Utils-bindings.js

    COMMAND

    ${CMAKE_CXX_COMPILER}

    --bind

    “${CMAKE_CURRENT_SOURCE_DIR}/base/emscripten.cc”

    -o

    Utils-bindings.js

    DEPENDS

    “${CMAKE_CURRENT_SOURCE_DIR}/base/emscripten.cc”

    )

  target_link_options(${Utils_TEST} PUBLIC --bind --post-js Utils-bindings.js)

 

Which generates these commands:

 em++ --bind base/emscripten.cc -o Utils-bindings.js

You probably want  to use `-c` here to compile `base/emscripten.cc` into an object file, and the link that object file into your final binary.

Otherwise you are asking emscripten to produce a filly linked program here, that that cannot be combined into another emscripten program.

 

em++  -s DISABLE_EXCEPTION_CATCHING=2 -s WASM=1 -s SAFE_HEAP=1 -s WARN_UNALIGNED=1 -fsanitize=undefined -Oz -s ASSERTIONS=1 -s DEMANGLE_SUPPORT=1 -g -Wall -fno-omit-frame-pointer -m32 --bind --post-js Utils-bindings.js @CMakeFiles/Utils-test_g.dir/objects1.rsp  -o Utils-test_g.html @CMakeFiles/Utils-test_g.dir/linklibs.rsp

Loading Utils-test_g.html in a browser produces the error.  I’ve tried all of the --(extern-)?(pre|post)-js permutations without success.  I’m well out of my depth and have been trying whatever I can find at this point.  How do I get these library bindings “linked” into the “executable”?  

Thanks!

~Michael Iatauro

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